1. Field of the Invention
The present invention relates to rack-mounted electronic systems and equipment racks.
2. Background of the Related Art
Some electronic systems are designed for servicing a large population of users, such as employees of a large corporation, residents of a town, or even a global network of users. Common examples include a telecommunications system operated on behalf of a town for providing local telephone service to its residents, and a large system of computer servers used by an Internet search engine to process a large volume of search queries from users worldwide. An electronic system with sufficient power and resources to service such large workloads may be assembled from many units of modular electronics equipment. The computer servers, telecommunications devices, and other electronic equipment used in these systems can be consolidated in a particular location for centralized administration. In a data center, for example, electronic equipment is typically housed in standardized racks and rack-mountable equipment enclosures. A number of these racks are commonly placed in a data center and arranged side-by-side in rows that form alternating hot-aisles and cold-aisles for efficient cooling of the equipment.
An equipment rack commonly includes a plurality of mounting and alignment substructures that facilitate mounting various devices in the rack. For example, a rack typically includes vertical rails and horizontal rails for directly mounting individual devices or mounting support structures, such as shelves, drawers, and chassis, which in turn support the devices. The rack and various rack-mountable electronic equipment may be constructed according to an industrial standard set forth by a trade organization, such as the Electronic Industries Alliance (EIA). (While the EIA trade organization ceased operations in 2011, the EIA standards are still recognized in the industry and managed by surviving trade organizations.)
Dimensional constraints are imposed by industry rack standards to ensure uniformity and compatibility of racks and rack-mounted devices. An EIA “19-inch” rack, for example, requires vertical rails having a minimum width of 16.7 mm and a distance of 450 mm between opposing vertical side rails. This yields an overall width of nominally 483 mm (19 inches) from the outer edge of one vertical rail to the outer edge of the opposing vertical rail. The rack, itself may be wider than 19 inches. Rack-mountable devices according to this standard have one dimension that is 19 inches to the end of mounting flanges, and another dimension that is some integer multiple of a unit length known as “1U” that is nominally 1.75 inches (44.45 mm). For example, a 1U server or other device has a height or width of 1.75 inches, a 2U server has a height or width of 3.5 inches, and so forth. Although these dimensional constraints provide compatibility and uniformity, they also present some design challenges in order to comply with specific dimensional constraints.